Evening all I currently have a 2.5 inch straight through exhaust with a sportscat downpipe and was thinking of changing and going for a 3 inch straight through exhaust and keeping the same downpipe, If I do change am I likely to get more BHP and Torque or is it just a myth and there is no difference whatsoever between the 2 and if there is a difference what exhausts do you all recommend?

 

There will be an optimum dia which is most efficient for venting gasses while retaining back pressure. I have no idea what it is though ;D

 

I was told by a friend that it is a myth that engines need back pressure, dont know how much truth there s in that...

 

i beleive its between 2" - 2.5" so stick with what youve got or you could lose the back pressure Gutmann pug is talking about